Heat sinks conduct thermal energy away from a heat-generating component to the environment by convection, radiation, or further conduction. Heat sinks usually have an extended surface area to improve heat dissipation to the environment. Aluminum (or other metal such as copper) extrusions are a common form of heat sink. These extrusions have a rigid base and extended surface area fins. The metal heat sinks are normally electrically conductive, and may contribute to electromagnetic interference problems in electronic devices. Other versions of metal heat sinks include flexible copper foils in various shapes, which optionally may have electrically insulating coatings on one or both major surfaces. Ceramics, metal, and sintered heat sinks are generally rigid.
Thermally conductive polymers have been used in heat exchangers, electronic devices, bipolar plates, and thermal interface materials. Injection molded heat sinks formed from high modulus thermoplastic or epoxy materials containing dispersed conductive particles have been described, as have composite heat sinks consisting of polymer fins laminated with metal foil. Non-metallic heat sinks can reduce interference problems with electromagnetic and radio frequency fields.